This invention relates to a method for producing images and more particularly to the silver complex diffusion transfer process, photographic materials for use in such process and method for producing same.
In more detail, it is concerned with a method for producing images of high density with an extremely small amount of silver halide and materials for use in such method.
The principle of the silver complex diffusion transfer process (DTR process) is described in U.S. Pat. No. 2,352,014 and is known.
According to the DTR process, a silver complex salt is imagewise transferred by diffusion from silver halide emulsion layer into image receiving layer, where it is converted to a silver image usually in the presence of physical development nuclei. For this purpose, a silver halide emulsion layer imagewise exposed is arranged or brought in contact with an image receiving layer in the presence of a developing agent and a silver halide complexing agent to convert unexposed silver halide to a soluble silver complex salt.
At the exposed areas of the silver halide emulsion layer the silver halide is developed (chemical development) and so is no longer dissolved and cannot diffuse.
At the unexposed areas of the silver halide emulsion layer the silver halide is converted to a soluble silver complex salt and is transferred into the receiving layer, where it forms a silver image usually in the presence of physical development nuclei.
The actions of silver halides at exposed and unexposed areas are opposite in direct positive silver halide emulsions.
The DTR process may be applied to various uses such as reproduction of documents, making of block copying material, instantaneous photographs, etc.
As mentioned above, the DTR process includes the so-called "two-sheet" type where silver halide emulsion layer and image receiving layer are provided on separate supports and they are brought in contact with each other at the time of diffusion transfer development to produce silver image in the image receiving material and the so-called "mono-sheet" type where the emulsion layer and the image receiving layer are provided on a same support usually in contact with each other. Both types may be used for block copying materials.
Generally, the light sensitive materials used for the DTR process contain a relatively small amount of silver as compared with those used for the ordinary chemical development. Even so, actually, the amount of silver used reaches about 8-15 millimols or more per 1 m.sup.2 of the light sensitive materials so as to obtain high density and to assure and retain the various characteristics as commercial products demanded by users, e.g., high contrast, high sharpness, etc. It has been generally difficult to reduce the amount of silver to less than half of said amount.
However, effective utilization of resources has been demanded not only in Japan which is poor in resources, but on a worldwide scale and photographic techniques which require silver in an amount as small as possible have been desired from the point of economy, too.